The majority of studies have indicated that bariatric surgery is an alternative for improving glucose and lipid metabolism. The remission of diabetes correlates with weight reduction . Bariatric surgery is an excellent solution to diabetes remission and weight reduction in most cases . However, only a few studies have researched the impact of sleeve gastrectomy on prediabetes. In this study, the changes in glucose, lipid profile, and bile acids in prediabetes patients who underwent LSG were explored and discussed.
A large meta-analysis  and recent observational studies  proved that improvement in glucose metabolism had a correlation with weight reduction. Similarly, a reduction in food intake capacity via bariatric surgery aided in weight loss herein, seen as continuous weight loss in nondiabetic patients, diabetic patients, and prediabetic patients during the course of a year postoperatively. In terms of glycaemic status, as expected, the initial HbA1c and fasting glucose of prediabetic patients appeared to be significantly different from those of nondiabetic patients alone and T2DM patients alone. Improvement in glycaemic control and body weight in prediabetes and diabetic patients began at the first month postoperatively and persisted in the next 12 months. This result corresponded with the findings of Rubio-Almanza et al., who suggested that bariatric surgery improves glycaemic control and obesity comorbidities in prediabetes patients . In addition, nearly 70% of prediabetes cases in our centre were treated by LSG. Within the course of the study, remarkable improvement in glycaemic state was observed in both diabetic patients and prediabetic patients. LSG is therefore an effective alternative for prediabetes patients, who fail to be managed by lifestyle modification, to assist with both weight loss and glycaemic control, thus delaying and preventing the progression of T2DM . The advantage of LSG is its minimal invasiveness, relatively low risk, few complications, and cost effectiveness; moreover, LSG is highly effective in delaying and preventing obesity and T2DM comorbidities and irreversible neurovascular complications in advance . Hence, LSG shall be encouraged in pre-diabetics. However, our study was a short-term follow-up study, and long-term follow-up will be continued and necessary, especially because these favourable results are related to weight loss.
Epidemiological and clinical studies have not only shown that HDL-C is negatively correlated with the incidence of atherosclerosis-related disease but also have recently suggested that some effects of bariatric surgery take place rapidly after surgery, as they may involve increased HDL levels [25-27]. Similarly, HDL, ‘good cholesterol’, was significantly increased in prediabetic patients after 6 months of the LSG operation. Increased HDL is thought to be associated with improved hepatic insulin sensitivity . This may explain the improved glycaemic status after bariatric surgery. Further research may be necessary to reveal the mechanism by which HDL affects glucose metabolism.
Bile acids are derivatives of cholesterol synthesized in hepatocytes; thus, bile acid synthesis is a regulator of body cholesterol. The initial mean concentration of TBA in diabetic and prediabetic patients was 3 µmol/L higher than that in Western patients [29-32]. The cause of high bile acid levels remains unclear. Fatty liver, race, glycaemic control or lipid profile may possibly contribute to the cause, resulting in compensatory bile acid secretion. Bile acid levels in prediabetic patients were significantly reduced by the first year postoperatively. Some studies have indicated that an increase in bile acids strongly correlates with an improvement in glucose and lipid metabolism [29, 30], but Robert E et al.  did not support the hypothesis that bile acids are key mediators of the early increase in postprandial GLP-1 and PYY secretion for improvement in glucose metabolism in postbariatric patients. In addition, Hilde Risstad et al.  indicated from data that bile acids had no significant change in 1-year postbariatric patients but significantly increased after 5 years. It has been proven that bile acids are not key mediators for the improvement of glucose in early postbariatric patients. Similarly, our results do not suggest that bile acids contributed to the rapid improvement in glycaemic control seen shortly after surgery.
Regarding lipid changes, this study revealed that triglycerides (TGs) continued to significantly decrease. Because bile acids are synthesized and secreted by hepatocytes, liver function directly affects the synthesis of bile acids. Clinically, ALT and AST are sensitive indicators of liver damage. ALT and AST were reduced in this study, indicating an improvement in liver function after metabolic surgery. Additionally, there is a correlation between the change in bile acid and ALT in prediabetes patients.
Some limitations should be noted in this study. First, bariatric surgery is still in the developing stages in China, and regular postoperative follow-up has not received close attention in some patients, resulting in a high rate of loss to follow-up. Thirty-five percent of the patients were followed up at 1 year postoperatively in this study; therefore, a small postoperative sample size was shown. In addition, our study was a short-term follow-up study, but long-term follow-up will be continued. Third, our results only reveal some clinical phenomena, and further research is necessary to consider prediabetes as a criterion for metabolic surgery and long-term effects after metabolic surgery.